Oxide composite particles, method for producing same, and resin composition

Abstract

Provided are oxide composite particles closer to a sphere that are mixed with a resin to obtain a resin composition having low dielectric constant and low dielectric loss tangent. The oxide composite particles containing silica and an oxide of aluminum (a single oxide or a composite oxide, or both), in which the oxide composite particles contain 10 to 90% by mass of an α-cristobalite crystal phase, 50% by mass or less of an α-alumina crystal phase, and more than 10% by mass of a mullite crystal phase, and an elemental ratio of aluminum to silicon (aluminum/silicon) as determined by X-ray photoelectron spectroscopy is 0.1 or more.

1 . Oxide composite particles comprising silica and an oxide of aluminum (a single oxide or a composite oxide, or both), wherein
 the oxide composite particles contain 10 to 90% by mass of an α-cristobalite crystal phase, 50% by mass or less of an α-alumina crystal phase, and more than 10% by mass of a mullite crystal phase, and   an elemental ratio of aluminum to silicon (aluminum/silicon) as determined by X-ray photoelectron spectroscopy is 0.1 or more.   
     
     
         2 . The oxide composite particles according to  claim 1 , wherein a content of the aluminum contained in the oxide composite particles is 5 to 60% by mass in terms of a single oxide of aluminum (Al 2 O 3 ). 
     
     
         3 . The oxide composite particles according to  claim 1 , wherein an average particle diameter of the oxide composite particles is 0.5 to 70 sm. 
     
     
         4 . The oxide composite particles according to  claim 1 , wherein an average circularity of the oxide composite particles is 0.85 or more. 
     
     
         5 . The oxide composite particles according to  claim 1 , wherein the oxide composite particles contain 0.1 to 50% by mass of the α-alumina crystal phase. 
     
     
         6 . A method for producing the oxide composite particles according to  claim 1 , the method comprising the steps of:
 mixing silica particles having an average particle diameter of 0.5 to 10 μm and alumina particles to obtain a mixture; and   heating the mixture at 1300 to 1700° C. for 2 to 8 hours.   
     
     
         7 . The method for producing the oxide composite particles according to  claim 6 , wherein the step to obtain a mixture is a step of spraying an alumina slurry containing the alumina particles into an air stream in which the silica particles are floating using a tumbling fluidized bed machine to form particles having a core-shell structure such that the alumina particles adhere to a surface of the silica particles. 
     
     
         8 . A resin composition comprising the oxide composite particles according to  claim 1  and a resin. 
     
     
         9 . The resin composition according to  claim 8 , wherein a content of the oxide composite particles in the resin composition is 20 to 80% by mass. 
     
     
         10 . The resin composition according to  claim 8 , which is a resin composition for high-frequency substrates.